x11vnc: first pass at client-side caching, -ncache option.

1 files changed, 26 insertions, 0 deletions

diff --git a/x11vnc/help.c b/x11vnc/help.c
index 6f7e803..73d5c86 100644
--- a/x11vnc/help.c
+++ b/x11vnc/help.c
@@ -2014,6 +2014,32 @@ void print_help(int mode) {
 "                       text selection, and some menu traversals.  It overrides\n"
 "                       any -pointer_mode setting.\n"
 "\n"
+#ifndef NO_NCACHE
+"-ncache n              Client-side caching scheme.  Framebuffer memory \"n\"\n"
+"                       (an integer) times that of the full display is allocated\n"
+"                       below the actual framebuffer to cache screen contents\n"
+"                       for rapid retrieval.  So a W x H frambuffer is expanded\n"
+"                       to a W x (n+1)*H one.  Use 0 to disable.  Default: XXX.\n"
+"\n"
+"                       This is an experimental option, currently implemented\n"
+"                       in an awkward way in that in the VNC Viewer you can\n"
+"                       see the cache contents if you scroll down, etc.  So you\n"
+"                       will have to set things up so you can't see that region.\n"
+"                       If this method is successful, the changes required for\n"
+"                       clients to do this less awkwardly will be investigated.\n"
+"\n"
+"                       Note that this mode consumes a lot of memory, both\n"
+"                       on the x11vnc server side and on the VNC Viewer side.\n"
+"                       If n=2 then the amount of RAM used is roughly tripled\n"
+"                       for both x11vnc and the VNC Viewer.  As a rule of\n"
+"                       thumb, note that 1280x1024 at depth 24 is about 5MB of\n"
+"                       pixel data.\n"
+"\n"
+"                       Because of the way window backingstore and saveunders\n"
+"                       are implemented, n must be even.  It will be incremented\n"
+"                       by 1 if it is not.\n"
+"\n"
+#endif
 "-wireframe [str]       Try to detect window moves or resizes when a mouse\n"
 "-nowireframe           button is held down and show a wireframe instead of\n"
 "                       the full opaque window.  This is based completely on\n"